In a field of a semiconductor chip, a liquid crystal display device and other electronic devices, along with the devices getting highly integrated, a decline of quality caused by fine particles (even a size of 0.1 μm or so matters), water and organic substances, etc. being mixed therein in the production procedure has been a major matter. Therefore, storage and carrying of a silicon wafer substrate, liquid crystal display substrate and other precision substrates used for producing the devices have to be under an environment where the above contaminating substances are reduced as much as possible.
Thus, a process for storing and carrying these precision substrates by keeping them in an airtight container wherein the inside is highly cleaned to be in a state of being isolated from an outside environment is used.
Also, to prevent fine particles and other contaminating substances from adhering to a precision substrate housed in the container, inside the container was filled with a clean air or an inert gas, however, demands for less contamination have become furthermore stronger in recent years, so a method of making the inside a vacuum or reduced pressure state has been proposed. A container, an inside thereof is in a reduced pressure or vacuum state, is required to be highly airtight and pressure tight, moreover, not to emit water, organic substances and other contaminating substances from the container itself. A metal container is known as a container satisfying the demands.
However, a metal container is heavy, a precision substrate inside cannot be observed, and the production cost is high. Thus, studies have been pursued for obtaining a container satisfying the above demands by using a thermoplastic resin.
A molded item of a thermoplastic resin generally releases water and organic substances, however, it is known that a container made by a cyclic olefin resin gives small contamination on its contents (the Japanese Unexamined Patent Publication No. 11-74337).
However, even the technique described in this publication is insufficient to deal with the recent demands for less contamination.